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From Vision to Reality: Revisiting The Cornerstone Group's Rooftop Farm

Last spring, I wrote about my visit to Cornerstone Rooftop Farm in Richfield, Minnesota, a pilot project of The Cornerstone Group, a real-estate management and urban-planning group, among other things. At that point, they had plans, hypotheses, and growing structures, but not yet any produce.

A few months ago, in late August, I revisited the property. As I walked with Colleen Carey and Ben Hertz on the Kensington Park building's sidewalk, we passed things they'd only talked about last time: potato bins, a berry patch, and miniature apple trees. I also saw ever-bearing patches of kale, chard, and collard greens. All of these things could be viewed from new benches, and harvested by anyone who visited the shops. This was truly functional landscaping -- beautiful to look at and edible to boot. I noticed no ripe strawberries, so someone (or something) had already enjoyed those.

Before we visited the farm again, Ben showed me the cooler he'd take to Lucia's restaurant that day, filled with Cornerstone produce: a variety of peppers, orange mint, chard, eggplant, carrots, beet greens and nasturtiums, which are edible flowers. Future coolers would have radishes and pattypan squash. Chef and local food advocate Lucia Watson was a partner in the project before the first seed sprouted. She is even more enthusiastic as the season comes to an end:

"We could not have had more fun or a higher quality product form our roof friends! We got the most beautiful precious peppers, herbs, tomatoes, assorted greens, little carrots (among other crops) AND we got to go and smash open the potato bins in the fall and harvest the urban potatoes. The produce came in re-useable mesh bags and were delivered sometimes twice or three times a week."

Also popular in the kitchen at Lucia's were the heirloom Alma Paprika peppers. One of the chefs smoked, preserved and dried these peppers to make her own paprika, which she'll uses in dishes on the menu throughout the year.

The heirloom peppers did very well, but their cousins the tomatoes weren't so lucky. This spring, in addition to a lot of moisture, there were swarms of aphids. The heirloom varieties of the tomatoes proved particularly susceptible to their unwanted attention. Next year, the Cornerstone Team and their farming partners from Ecological Gardens will try non-heirloom varieties and other pest management solutions including insects like ladybugs. Cornerstone initially had an insectory as part of the rooftop farm, but they removed it when the city of Richfield asked them to scale back. Cornerstone is hoping to try again next year, armed with this year's experience and an education on the risks (few) and benefits (many) of an insectory, including potentially saving the tomato crop.

The Cornerstone team worked in tandem with the farmers from Ecological Gardens. When the Cornerstone team worked to their strengths -- strategy, planning, and problem solving -- and the farmers worked to monitor and tend the farm, things went very well. Like a typical farm, rather than a garden, the crops required more work and more technical monitoring than what the Cornerstone staff could supply on a non-regular basis. Last spring, the Cornerstone staff thought they'd have a very hands-on part in the farming. But important tasks like when to water, how much, and how to monitor the crops worked better with fewer people involved.

The planters they chose to try, sip containers and earth boxes, both worked very well. Having these mobile, modular planters allowed them to experiment with different placements and irrigation techniques. The herbs, such as lemongrass, lemon balm, thyme, and basil, did particularly well. Marigolds planted near them helped with pest control. This year, the rooftop farm's sip containers, earth boxes, and protective hoop structures extended the growing season beyond what a traditional farm in Minnesota's bioclimate could do. Even now, in early November, they have a variety of autumn greens and herbs. The team hopes to be growing into December too.

With their learnings, the Cornerstone team hopes to farm on a larger scale in the future; the Kensington rooftop is almost at capacity. Their ideal size would be one acre, but it's difficult to find an existing roof that can be adapted for such a large farm. This is the main challenge Dayna Burtness of Skyhigh Harvest ran into this year. Like Cornerstone, she wanted to bring rooftop farms to Minneapolis, as is being done in Chicago, New York, and cities in California. Unfortunately, retrofitting existing roofs for gardens is challenging both for physical and zoning reasons. Building construction slowed along with the economy, so there aren't many new construction sites to use. When the building industry is on the upswing, though, green roofs, in both the metaphorical and literal senses, will be part of the plan.

Cornerstone's rooftop experiment was a success. Not only did it return meaningful results, but also lots of excellent quality produce. By blazing a trail on the roof -- and finding new growing space where there was none -- the Cornerstone Group has shown what can be done as things are. It's exciting to imagine what might be done with a new generation of greener buildings.